Muffler



July 25, 1938 G. c:A STARKWEATHER 2,124,933

.MUFFLER Filed June 14, 19:57

2 Sheets-Sheet l Y M im @um l.

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July 26, 193s. l

G. C. STARKWEATHER MUFFLER 2 Sheets-Sheet 2 Filed June 14, 1937 K m M m Patented July 26, 1938 UNITED STATES PATENT GFFECE MUFFLER falo, N. Y.

Application .lune 14, 1937, Serial No. 148,967

8 Claims.

This invention relates to improvements in muillers or silencers of the kind which are usable for reducing the noise of the exhaust of internal combustion engines.

In the Starkweather and Haas Patent Nos. 2,047,442 and 2,047,443 are shown muilers in which restrictions in the inner periorate conduit are provided between groups of perforaticns communicating with a chamber in such a manner that the restriction in the conduit causes a portion of the gases to by-pass the restriction by passing into the chamber through apertures located in iront of the restriction and returning from the chamber through the conduit through apertures located in rear of the restriction. I have found that by locating the restriction in rear of all of or most of the openings or apertures communicating with a chamber, a different operation of the chamber is produced in that substantially no by-passing of gases or sound waves around the restriction results. Consequently, by locating the restriction in this manner, the gases which are forced into the chamber because of the slight increase in pressure created in advance of the restriction must reverse their direction of flow and then re-enter the chamber through the same openings or apertures in advance of the restriction. While the arrangement of the restriction in the conduit as herein described produces a somewhat increased back pressure in the muiiier than that described in said patents, yet the modified action of the silencing chambers arranged about the conduit makes the use of this arrangement of the restriction desirable for certain purposes.

One of the objects of this invention, therefore, is to provide a muffler of the type having a main gas passage and chamber communicating therewith with a restriction arranged in the gas passage in rear of the connection or opening communicating with the chamber in such a manner as to provide for a backing up of the gases into such chamber' and a consequent return of the gases through the apertures into the conduit in advance oi the restriction. Another object of this invention is to provide a muiiler in which the effectiveness of chambers arranged about a perforate conduit is increased or modified by means of restrictions located in the conduit in rear of all of the apertures or openings leading to such chamber. Other objects of this invention will appear from the following description and claims.

In the accompanying drawings:

Figs. l and 2 are longitudinal central sections of two diiierent forms of mulers embodying this invention.

Fig. 3 is a longitudinal central sectional View of the iront portion of a muiller of modified construction.

Fig. 4 is a similar longitudinal central section of the remainder or rear portion oi the muiier shown in Fig. 3.

Figs. 5 and 6 are respectively transverse sectional views, taken respectively on lines 5 5 and 66, Fig. 3.

In all of the muiilers shown, the outer casing or housing of the muliler may be of any suitable or desired construction, such for example as an outer shell A provided at one end with an inlet head B having an inlet formed therein, for ex ample, by means of an integral tubular duct b to which the exhaust pipe of an engine may be secured in any suitable or usual manner. At their other ends these outer shells A are provided with exhaust or discharge heads C having suitable discharge openings formed by means of integral ducts c through which the gases are discharged from the muiiiers and to which the usual tail pipes may be connected, if desired.

In Fig. l, I have illustrated my invention as applied to a comparatively simple form of muffler, in which the passage for gases through the muliler consists of an inner perforate conduit E in which openings for the flow of gases out oi and into the conduit are in the form of perforations 9, which may, for example, be produced by forming in the conduit 8 longitudinally extending slits and by bending the metal at one side of each slit outwardly to form louvers. Any other form of aperture or opening may, however, be prcvided if desired, and preferably these apertures or openings are arranged in groups, the groups being in turn arranged at intervals lengthwise of the conduit 8. About the exterior of the con duit 8, suitable sound deadening chambers may be provided in any suitable or desired manner. For example, a chamber It) may be formed between the inner conduit and the outer shell A by means of a transversely extending wall or bale l l extending from the conduit to the outer shell. At the rear end of the muler, high irequency resonator chambers i4 and l5 may be provided about the conduit S by means of an intermediate shell of any suitable or desired form, that shown being formed by two half shells I6 and Il, the longitudinal edges of which are suitably secured together as indicated in broken lines at I8 and these two shell sections are provided with inwardly extending shoulders or parts I9 which engage the conduit 8 and thus enclose perforate portions or groups of perforations of the conduit and form chambers which react upon high frequency sound waves in such a manner as to render them inaudible.

The construction described also results in the formation of another chamber 2B within the muiller which includes a portion which is arranged between the conduit and the outer shell A and another part which extends into the space between the intermediate shell I6, II and the outer shell I8.

In order to provide for a more pronounced and modified action of the chambers I0 and 20 upon gas pulsations and sound Waves in the muilier, I have provided restrictions in the interior of the conduit, which are located in rear of all or substantially all of the openings or apertures in the conduit communicating with the respective chambers. 'I'he restrictions employed may be of any suitable or desired form and may be formed integrally with the conduit or they may be in the form of sleeves inserted in the conduit, both of which forms of restrictions are disclosed in the aforementioned Starkweather and Haas patents. In the particular muier shown in Fig. l, I have illustrated by way of example, a pair of restricting sleeves 2l and V22'each of which has a cylindrical portion tting snugly within the interior of the conduit 8 and rigidly secured thereto, for example by welding, and also a portion of reduced diameter. Any other form of restriction may, however, be employed ,if desired. In accordance with my invention, I locate the restriction 2l in rear of all openings or apertures leading into the chamber III and similarly the restriction 22 is located in rear of all apertures or openings leading into the chamber 20.

By means of the construction described, gases entering the inlet of the muffler housing pass into the conduit 8 and are held back to a limited extent by means of the restriction 2| in the conduit,V so that substantial portions of the peaks of pressure pulsations enter into the chamber Ill through the perforations or apertures 9 of the conduit, and the gas flowing through these apertures into the conduit probably also carries sound waves with it. The remainder of the pressure pulsations continue through the restriction 2| into the portion of the conduit 8 in rear thereof and are again held back to a limited extent by the restriction 22, so that further portions of the peaks of pressure pulsations, probably accompanied by sound waves, will enter into the chamber 20.

In` the case of gases flowing into the chambers I and 20 through the apertures S in the conduit, these gases will be forced in general to reverse their direction of movement, and thus return through the same apertures through which these gases entered the chambers Ill and 2l), and will pass back into the conduit 8., during the troughs or intervals between the peaks of the pressure pulsations, thus equalizing to a material extent the fiow of gases in the conduit. Because of the fact that the location of the restrictions 2| and 22 is in rear of the apertures leading to the chambers Ill and 2U respectively, it will be impossible for gases entering the apertures to by-pass around the restrictions 2| and 22 as in the before mentioned patents, and consequently, a complete reversal of the flow of gases entering the chambers I0 and 20 is necessary. This action, con- Y through apertures 24.

sequently, results in a different action of the chambers I0 and 20 upon the gases and sound waves in the muilier, than takes place in the before mentioned patents, in which the restrictions eifect a bypassing of the gases.

After passing through the restriction 22, the gases now through the portion of the conduit which is enclosed by the high frequency resonator chambers I4 and I5 where a further effective silencing of sound waves results in a well known manner.

In the muiller shown in Fig. 2, the space between a perforate inner conduit 25 andthe outer shell Aris divided into a plurality of chambers by means of transversely extending walls or bales 26, 2l and 28, thus forming chambers 29, 30, 3l and 32, all of which communicate with the interior of the conduit 25 by means of suitable apertures or openings 22 in the conduit 25. In the conduit 25 are arranged a pair of restrictions 33 and 34, which are located in rear of those perforations which' communicatewith the chambers 2S and 3i) respectively. It will be readily understood from the description of the operation of the muiiler shown in Fig. l, that a similar operation will take place in connection with the muilier shown in Fig. 2, namely, that gases owing lengthwise of the conduit will encounter an increased resistance at the restriction 33V, and thus build up in advance of the restriction a slightly increased pressure which causes gases to flow into the chamber 29 to a materially greater extent than would be the case, if the restriction 33 were not present. The gases entering the chamber 29 must be reversed in their direction of flow and pass back into the conduit 25 through the same group of apertures through which they entered. A similar action results in the chamber 30, and the gases which` finally pass through the restriction 32 will, consequently, be of relatively uniform iiow and this flow will be still more equalize-d by means of the chambers 3l and 32 which also communicate with the interior of the conduit 25 It will be obvious that any desired number of restrictions may be employed, if desired, and consequently, restrictions could also be employed in connection with the chambers 3| and 32, and in some cases, only a single restriction may be necessary to produce the desired silencing effect.

In Figs. 3 to 6 inclusive, I have shown my invention applied to a muler having an inter' mediate shell. In this Inuiiler, o represents the inner conduit having suitable openings or perforations SI therein, which may be produced by forming a series of longitudinal slits in the conduit Lll and pressing the metal at one side of each slit outwardly to form louvers 39, as shown in Fig. 6. IThe conduit shown connects at one end with the inlet b and at the other end with the outlet or discharge c. i3 represents an intermediate shell of any suitable or desired form which may be supported in the muiiier in any suitable manner. In the construction illustrated, the intermediate shell i3 is shorter than the conduit Il and is supported from the conduit intermediate of its ends by means of a series of transverse partitions or baffles 443, 45 and 46, and the ends of the intermediate shell are provided with suitable openings communicating with outer or low frequency resonator chambers i8 and @9, these chambers being separated from each other by means of a transverse partition or baiie 59 connecting the outer shell A with the intermediate shell 43. The openings in the intermediate shell may be formed sof in any suitable or desired manner, and in the construction illustrated by way of example, I leave at least portions of the ends of the intermediate shell open, other portions I being pressed inwardly into engagement with the conduit Q5, these pressed-in portions being spaced between open portions of the intermediate shell which are spaced from the conduit 4U and form therewith channels or passages 52, which act as bottle necks in connection with the resonator chambers 58 and 59. Any other means for establishing communication between the interior of the end portions of the inner shell and the chambers 43 and i9 may be provided, if desired. It will be noted that the transverse baies 44, 45 and 45 form in the space between the conduit and intermediate shell, high frequency resonator chambers, while the portions of the intermediate shell between the ends of this shell and the transverse baffles i4 and 66 form chambers 54 and 55 which connect with the outer resonator chambers 58 and 39.

In order to increase the effectiveness of the outer chambers 5i! and e9, I provide in the inner conduit d5 restrictions 5S and 5?, which are located in rear of those perforations which open into the end chambers 54 and 55 of the intermediate shell.

In the operation of the muffler described, gas pulsations entering into the inner conduit @D will be slightly checked by the restriction 56 so that a substantial portion of each pressure pulsation will now outwardly through the apertures 4I into the chamber 54 and then through the openings or channels 52 into the outer low frequency resonator chamber 58. Since the gases cannot by-pass the restriction 55 as is the case in the muillers shown in the patents hereinbefore referred to. a higher pressure will accumulate in the end chamber 55, thus forcing a larger proportion of gases to flow into the outer chamber 48 than would be the case, if the restriction 545 were not employed. The reversing of the ow of gases in the end chamber of the intermediate shell and the outer chamber 48 also requires a slightly longer time interval than the by-passing of gases, so that the gases will return to the interior of the conduit til after a greater time interval than would be the case with a corresponding gas pressure pidsation in the mufliers described in the aforementioned patents. The increased delay in the return of gases into the conduit may be utilized advantageously in connection with the design of muflers for certain types of engines.

The gases, after passing through the restriction 5S, pass the high frequency chambers formed between t'ne baiiies 4e, l5 and 46, and then reach the restriction 5l in which a similar action takes place, as has already been described in connection with the restriction 56. The gases passing out of the apertures in the conduit in advance of the restriction 5'? find their way through the chamber and the passages 52 into the outer chamber 49.

While the accompanying drawings illustrate only three forms of muiflers embodying my improvements, it will be obvious that restrictions positioned in accordance with this invention may be employed in inumers of many different forms and constructions and may be used in any type of murlcr conduit through which all or a greater portion of t. e gases entering the muffler pass.

The restrictions herein described are inexpensive to produce and may be easily provided in any muffler conduit having communication in advance of the restriction with a chamber, and while the restrictions increase to some extent the back pressure of the niuiiler, such increase in back pressure is more than compensated for by the materially increased silencing obtained. The restrictions may, of course, vary in the extent to which they restrict the passage of gas through the conduits in which they are located by varying the internal diameters of the reduced portions thereof, and also the silencing effect may be varied to some extent by varying the sizes of the restrictions.

I claim as my invention:

il.. A muiiler having a housing provided with an inlet and an outlet, a perforate conduit of substantially uniform diameter connecting said inlet and said outlet and arranged Within said housing, a partition arranged in the space between said housing and said conduit and forming a chamber' winch communicates with the interior of said conduit through perforations therein, and a restriction in said conduit arranged in rear of all of those perforations communicating with said chamber.

2. A muffler having a housing provided with an inlet and an outlet, a perforate conduit of substantially uniform diameter within said housing through which gases iiow, means arranged between said conduit and said housing and forming therewith a chamber into which gases may enter only through perforations of said conduit, and a restriction in said conduit located in rear of all of the perforations communicating with said chamber.

3. A muiiier having a housing provided with an inlet and an outlet, a passage within said housing through which gases flow from said inlet to said outlet and including a conduit of substantially uniform diameter, partition means arranged between said housing and said conduit and forming a substantially closed chamber having a connection with said passage through which gases may flow into and out of said chamber, a restriction in said conduit for restricting the flow of gas pulsations through the same and located rearwardly of said connection between said conduit and said chamber, whereby an increase in gas pressure in advance of said restriction produces an increased passage of gas into said chamber.

4. A muiiler having a housing provided with an inlet and an outlet, a passage in said housing leading from said inlet to said outlet and including a conduit of substantially uniform diameter, partition means arranged between said housing and said conduit and forming a chamber having a connection with said passage through which gases may flow into and out of said chamber from said passage, and a restriction in said conduit for restricting the iiow of gas pulsations through the same and located in rear of any connection between said passage and said chamber, whereby an increase in pressure in advance of said restriction results in increased ow of gases into said chamber.

5. A muffler having a housing provided with an inlet and an outlet, a perforate conduit of substantially uniform diameter arranged within said housing and connecting said inlet and outlet, a partition between said housing and said conduit and forming a substantially closed chamber those perforations communicating with said chamber, whereby increased pressure of gases in advance of said restriction-results in an increased flow of gases into said chamber, and

l whereby the gases in said chamber reverse their direction of movement and return through said perforations and re-enter said conduit through said perorations in advance of said restriction.

6. A muler having a housing provided with an inlet and an outlet, a perforate conduit oi substantially uniform diameter within said housing through which gases low, an intermediate shell between said conduit and said housing and form` ing with said conduit an innner chamber arranged about a perforate part of said conduit and an outer chamber communicating with said inner chamber, and a restriction in said conduit located in rear of all of the perforations in said conduit communicating with said inner cham- .y ber, saidrrestriction producing an increased gas pressure in said conduit in advance of said reinlet and an outlet, a passage in said housing about said conduit and a transversely extending leading from said inlet to said outlet and including a conduit of substantially uniform diameter, partition means arranged between said housing and said conduit and including a shell extending part forming an end wall in the space between said shell and said conduit, said partition means forming with said conduit aninner chamber having a connection with said passage and an outer chamber having a connection with said inner chamber, and a restriction in said conduit located in rear of any connection between said passage and said inner chamber, whereby an increase in pressure results in advance of said restriction, which produces an increased ow of gases and sound waves into said inner and outer chambers.

8. A muier having a housing provided with an inlet and an outlet, a perforate conduit of substantially uniform diameter within said housing through which gases flow, an intermediate shell betweenY said conduit and said housing, a transverse baie connecting said shell and said conduit to form with said shell an inner chamber about a periorate portion of said conduit, a transverse balile connecting said intermediate shell with said housing to form therewith an outer chamber communicating with said inner chamber, and a restriction in said conduit located in rear of all of the perforations in said conduit communicating with said inner chamber, said restriction producing an increased gas pressure in said conduit in advance of said restriction, which produces an increased passage of gases and sound waves into said inner chamber and from said inner chamber to said outer chamber.

GAIL C. STARKWEATHER. 

